Nylon 6, a polymer of caprolactam, is a well-recognized engineering plastic. As is characteristic of these materials, nylon is strong, is capable of withstanding considerable abuse, it has a low coefficient of friction, long wear life and makes an excellent bearing element.
Nylon does not age well in strong sunlight and it is conventional to fill it with a few percent carbon black for outdoor weathering applications. It is well recognized that carbon black prevents ultra-violet degradation in many polymers by scattering and absorbing damaging radiation and by acting as a free radical trap. UV protection is reported best achieved in carbon blacks in the 16 to 20 micrometer particle diameter range when well dispersed in concentrations between about 2 to 3 percent by weight.
Carbon black greatly improves the properties of many polymers such as rubber. This is not the case with nylon, however, and the addition of carbon black, even in small quantities much less than 1%, can significantly lower elongation, notched Izod, impact strength and other physical properties.
Accordingly, it is the object of this invention to provide a novel nylon composition that has good UV stability without unduly sacrificing physical property such as elongation, notched Izod and impact strength.